I know I'm not quite answering your post precisely but I'm pretty sure Jeckells at Wroxham would come down your way to measure up etc - I don't think you're out of the way for them at all.
I've used other people in the past but Jeckells' upholstery work is the best I've found and competitive for the quality you get.
Give EastcoastBernie a shout. She ( www.ritzystitches.com )makes all sorts of covers and things for boats. Had some dodgers made recently, top job. Done lots of work for other East Coasters too.